Resolved Problem receiving email after server restart

[smilan]

Server operating system version

CentOS Linux 7.9.2009

Plesk version and microupdate number

Obsidian v18.0.57

Recently I restarted VPS server hosted at Hetzner. First i could not access Plesk admin and Plesk update page, and I had to manually open permanent ports in CentOS with SSH.
I didn't have this problem before after server restart, the only difference is that I turned off Plesk firewall and I configured Hetzner firewall.
The problem I had now is that I can not receive emails anymore, I can still send emails, but server is not receiving email on any domain.
The strange thing is that everything was working perfectly before server restart.
I also manually added all the necessary ports in CentOS firewall.
Also switched from Postfix to QMail but no change in behavior, and tried to turn off "Enable SMTP service on port 587 on all IP addresses" function. I also tried to disable suexec as I read somewhere that in some cases this can be a problem.
Do you have any ideas? I did read other similar threads on the forum, and I already spent sometime trying to fix this.

CentOS Linux 7.9.2009
Plesk Obsidian v18.0.57
Hetzner VPS
Hetzner Firewall

 

[Peter Debik]

Maybe try to disable Hetzner firewall just to make sure it does not intercept traffic?

 

[smilan]

It is working now finally. I am testing other domains to know exactly what was wrong. I will share my findings.

 

[smilan]

Maybe try to disable Hetzner firewall just to make sure it does not intercept traffic?

I didn't use Hetzner firewall before, but I started all this changes because fail2ban and ModSecurity where giving me and my clients lots of headaches. It will ban user IP just from normal interaction. I first disabled fail2ban and ModSecurity, then I setup Hetzner firewall, but things started to go wrong.
Now I have Hetzner firewall up, and fail2ban, Ill se how it goes. Mail is working on one domain, now I will replicate, step by step, what I did to be sure what made the change. Most of the changes are in Hetzner DNS console.